Anterior Shoulder Instability

Anterior shoulder instability describes a spectrum from subtle subluxation (partial displacement) to recurrent dislocation of the humeral head out of the front of the glenoid socket. It is the most common direction of shoulder instability. After an initial anterior dislocation, the recurrence rate depends heavily on age at first dislocation — young active males have the highest risk (up to 90% recurrence by some estimates).

Episodes of the shoulder "going out" or feeling loose during overhead activities, apprehension with the arm in the throwing position (abduction, external rotation). Apprehension test with the relocation test are the hallmarks. CT arthrography or MRI arthrography quantifies glenoid and humeral head (Hill-Sachs) bone loss — critical for surgical planning.

Recurrent instability interfering with daily life or sport, young contact athletes after a first dislocation, and significant bone loss are indications for surgical stabilization.

External patient-education references and related OSI pages for additional background:

• Britannica — Dislocation
• Britannica — Shoulder (anatomy)
• AAOS OrthoInfo — patient education library
• OSI glossary — orthopedic terminology in plain language